Phosphorous containing glass having antimicrobial efficacy

ABSTRACT

A strengthened antimicrobial glass including greater from about 50.0 mol. % to about 65.0 mol. % SiO 2 , about 14.0 mol. % to about 22.0 mol. % Al 2 O 3 , about 14.0 mol. % to about 22.0 mol. % R 2 O, wherein R is an alkali metal, and about 4.0 mol. % to 10.0 mol. % P 2 O 5 . The glass may have a compressive stress layer having a thickness of greater than or equal to about 20 μm less than or equal to about 60 μm and having a compressive stress of greater than or equal to about 700 MPa. The glass may have an antimicrobial activity greater than or equal to about 1.0 log kill at about 23° C. and about 40.0% relative humidity. A method for making the glass may include obtaining a glass article, strengthening the glass article by contact with a first ion-exchange liquid, and contacting the glass article with second ion-exchange liquid comprising an antimicrobial agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/548,650 filed on Nov. 20, 2014, which claims the benefit of priorityto U.S. Provisional Application Ser. No. 61/908,828 filed on Nov. 26,2013, the content of which are relied upon and incorporated herein byreference in their entirety.

FIELD

The present disclosure is directed to phosphorous containing glasshaving antimicrobial efficacy and methods of making such glass. Inparticular, the disclosure is directed to a transparent, chemicallystrengthened glass with antimicrobial properties that may have afunctional coating on the glass that does not interfere with theantimicrobial efficacy of the glass.

Technical Background

Recently, the use both metallic silver particles and silver salts havebeen described in the patent and technical literature as a means forimparting antibacterial properties to a variety of materials. Silverions interact with a wide range of molecular processes withinmicroorganisms resulting in a range of effects from inhibition of growthand loss of infectivity to cell death (cytotoxicity). The mechanismdepends on both the concentration of silver ions that are present andthe sensitivity of the microbial species to the silver ions. Contacttime, temperature, pH and the presence of free water all impact both therate and extent of antimicrobial activity.

The prevalence of “touch screens” in contemporary society gives rise tomany surfaces that can harbor microbes, bacteria and viruses, and thesemicrobes can be transferred from person to person. Antimicrobialactivity at high relative humidity and physiological temperatures (e.g.,about 37° C.) is achievable. However, at ambient conditions (e.g., about42% relative humidity and about 23° C.) the efficacy of silver ionsdecreases. Accordingly, a need exists for a glass that has improvedefficacy of silver ions at ambient conditions.

SUMMARY

In embodiments, a strengthened antimicrobial glass is disclosed. Theglass may include greater than or equal to about 50.0 mol. % to lessthan or equal to about 65.0 mol. % SiO₂, greater than or equal to about14.0 mol. % to less than or equal to about 22.0 mol. % Al₂O₃, greaterthan or equal to about 14.0 mol. % to less than or equal to about 22.0mol. % R₂O, wherein R is an alkali metal, and greater than or equal toabout 4.0 mol. % to less than or equal to about 10.0 mol. % P₂O₅. Theglass may have a compressive stress layer that has a thickness ofgreater than or equal to about 20 μm less than or equal to about 60 μm,and a compressive stress of greater than or equal to about 700 MPa. Theglass may also have an antimicrobial activity greater than or equal toabout 1.0 Log Kill at about 23° C. and about 40.0% relative humidity.

In embodiments, a method for making strengthened antimicrobial glass isdisclosed. The method may include obtaining a glass article havinggreater than or equal to about 50.0 mol. % to less than or equal toabout 65.0 mol. % SiO₂, greater than or equal to about 14.0 mol. % toless than or equal to about 22.0 mol. % Al₂O₃, greater than or equal toabout 14.0 mol. % to less than or equal to about 22.0 mol. % R₂O,wherein R is an alkali metal, and greater than or equal to about 4.0mol. % to less than or equal to about 10.0 mol. % P₂O₅. The glassarticle may be strengthened by contact with a first ion-exchange liquid;and subsequently contacted with a second ion-exchange liquid comprisingan antimicrobial agent. The glass may have a compressive stress layerhaving a thickness of greater than or equal to about 20 μm less than orequal to about 60 μm, and a compressive stress of greater than or equalto about 700 MPa. The glass may have an antimicrobial activity greaterthan or equal to about 1.0 log kill at about 23° C. and a relativehumidity of about 40%.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments described herein, including the detailed description whichfollows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph showing results of a ring-on-ring test for glassarticles according to embodiments disclosed herein; and

FIG. 2 is a bar graph showing antimicrobial properties of glass articlesaccording to embodiments disclosed herein.

DETAILED DESCRIPTION

Embodiments disclosed herein are directed to phosphorous containingglasses having antimicrobial efficacy and methods for making suchglasses. In embodiments, The glass may include greater than or equal toabout 50.0 mol. % to less than or equal to about 65.0 mol. % SiO₂,greater than or equal to about 14.0 mol. % to less than or equal toabout 22.0 mol. % Al₂O₃, greater than or equal to about 14.0 mol. % toless than or equal to about 22.0 mol. % R₂O, wherein R is an alkalimetal, and greater than or equal to about 4.0 mol. % to less than orequal to about 10.0 mol. % P₂O₅. The glass may have a compressive stresslayer that has a thickness of greater than or equal to about 20 μm lessthan or equal to about 60 μm, and a surface compressive stress ofgreater than or equal to about 700 MPa. The glass may also have anantimicrobial activity greater than or equal to about 1.0 Log Kill atabout 23° C. and about 40.0% relative humidity. Methods for making suchglass articles are also disclosed in embodiments.

Glass Composition

In an exemplary glass composition, SiO₂ is the largest constituent and,as such, SiO₂ is the primary constituent of the glass network formedfrom the glass composition. Pure SiO₂ has a relatively low CTE. However,pure SiO₂ has a high melting point. Accordingly, if the concentration ofSiO₂ in the glass composition is too high, the formability of the glasscomposition can be diminished as higher concentrations of SiO₂ increasethe difficulty of melting the glass, which, in turn, adversely impactsthe formability of the glass. Low SiO₂ glasses, such as, for example,glass with less than 50 mol. % SiO₂, tend to have poor durability andresistance to devitrification, so it is practical to have more than 50mol. % SiO₂ for ease of forming.

In embodiments, the glass composition can comprise SiO₂ in aconcentration from greater than or equal to about 50 mol. % to less thanor equal to about 65 mol. %, such as from greater than or equal to about52 mol. % to less than or equal to about 63 mol. %. In otherembodiments, the glass composition can comprise SiO₂ in a concentrationfrom greater than or equal to about 55 mol. % to less than or equal toabout 60 mol. %, such as from greater than or equal to about 57 mol. %to less than or equal to about 58 mol. %.

The glass composition of embodiments can further comprise Al₂O₃ inaddition to SiO₂. Al₂O₃ can serve as a glass network former, similar toSiO₂. Al₂O₃ can increase the viscosity of the glass composition.However, when the concentration of Al₂O₃ is balanced against theconcentration of SiO₂ and, optionally, the concentration of alkalioxides in the glass composition, Al₂O₃ can reduce the liquidustemperature of the glass melt, thereby enhancing the liquidus viscosityand improving the compatibility of the glass composition with certainforming processes. In addition, Al₂O₃ can enhance the ion exchangeperformance of alkali silicate glasses.

In embodiments, the glass composition can comprise Al₂O₃ in aconcentration from greater than or equal to about 14 mol. % to less thanor equal to about 22 mol. %, such as from greater than or equal to about15 mol. % to less than or equal to about 20 mol. %. In otherembodiments, the glass composition can comprise Al₂O₃ in a concentrationfrom greater than or equal to about 16 mol. % to less than or equal toabout 19 mol. %, such as from greater than or equal to about 17 mol. %to less than or equal to about 18 mol. %.

Alkali metal oxides (hereinafter referred to as “R₂O” where “R” is oneor more alkali metals) may be added to lower the viscosity of a glass toimprove the meltability and the formability thereof. In addition, alkalimetal oxides may also enable ion exchange that modifies both the stressand refractive index profiles of the glass. When the content of R₂O istoo large, the thermal expansion coefficient of the glass becomes toolarge, and the thermal shock resistance of the glass may decrease. Inembodiments, the glass composition may include one or more of Li₂O,Na₂O, K₂O, Rb₂O, and Cs₂O as an alkali metal oxide. In some embodiments,the glass composition may include Na₂O and/or Li₂O as alkali metaloxides. In other embodiments, the glass composition may include Na₂O asan alkali metal oxide. In some embodiments, the glass composition do notcontain Li₂O or lithium from any other source.

In embodiments, the glass composition can comprise R₂O in aconcentration from greater than or equal to about 14 mol. % to less thanor equal to about 22 mol. %, such as from greater than or equal to about15 mol. % to less than or equal to about 20 mol. %. In otherembodiments, the glass composition can comprise R₂O in a concentrationfrom greater than or equal to about 16 mol. % to less than or equal toabout 19 mol. %, such as from greater than or equal to about 17 mol. %to less than or equal to about 18 mol. %.

Including a relatively high amount of R₂O in the glass composition mayallow enhanced ionic interdiffusion of small alkali metal ions and largealkali metal ions during standard ion exchange processes (e.g., ionexchange in a molten KNO₃ salt bath at about 410° C.). Without beingconstrained to any particular theory, it is believed that the relativelyhigh amount of R₂O may act as a charge compensator for Al³⁺, therebyforming charge balanced units tetrahedrally coordinated with oxygen.

To retain high indentation damage resistance, glass compositionsaccording to embodiments have a molar ratio of Al₂O₃ to R₂O of fromgreater than or equal to about 0.5:1 to less than or equal to about1.5:1.0, such as about 1.0:1.0. However, in embodiments where glasscompositions are required to have high amounts of R₂O and a ratio ofAl₂O₃ to R₂O of, for example, about 1:1, the balance of SiO₂ may not besufficient to make the glass composition compatible with zircon formingbodies at the forming temperature, potentially leading to the formationof zircon defects in the glass.

However, P₂O₅ may increase the zircon breakdown temperature.Accordingly, in embodiments, P₂O₅ may be substituted for SiO₂ toincrease the zircon breakdown temperature and allow glass compositionswith high R₂O contents and an Al₂O₃ to R₂O ratio of, for example, about1:1, to be compatible with zircon forming bodies. Without beingconstrained to any particular theory, it is believed that the 35 kPtemperature decreases and the zircon breakdown increases as the molarpercentage of SiO₂ decreases and the molar percentage of P₂O₅ increases.

In embodiments, the glass composition can comprise P₂O₅ in aconcentration from greater than or equal to about 4.0 mol. % to lessthan or equal to about 10 mol. %, such as from greater than or equal toabout 5.0 mol. % to less than or equal to about 9.0 mol. %. In otherembodiments, the glass composition can comprise P₂O₅ in a concentrationfrom greater than or equal to about 6.0 mol. % to less than or equal toabout 8.0 mol. %, such as about 7.0 mol. %.

The glass composition can, in some embodiments, contain other elements,such as alkaline earth metal oxides. In embodiments, the alkaline earthmetal oxides can be selected from MgO, CaO, SrO, BaO, and combinationsthereof. These oxides can be added to increase meltability, durability,and glass stability. In addition, alkaline earth metal oxides can beadded as stabilizers that help prevent degradation of the glasscomposition upon exposure to environmental conditions. While ZnO is notan alkaline earth, it is a divalent oxide and serves a similar functionas the above referenced alkaline earth metal oxides and, thus, ZnO canbe added to the glass composition to enhance the same properties asalkaline earth metal oxides. However, adding too much alkaline earthmetal oxide and/or ZnO to the glass composition can decrease itsformability.

In embodiments, the glass composition comprises alkaline earth metaloxide in concentrations from greater than or equal to 0.0 mol. % to lessthan or equal to about 4.0 mol. %, such as from greater than or equal toabout 1.0 mol. % to less than or equal to about 3.0 mol. %. In otherembodiments, the glass composition comprises alkaline earth metal oxidesin concentrations from greater than or equal to about 1.5 mol. % to lessthan or equal to about 2.5 mol. %. Similarly, in embodiments, the glasscomposition comprises ZnO in concentrations from greater than or equalto 0.0 mol. % to less than or equal to about 4.0 mol. %, such as fromgreater than or equal to about 1.0 mol. % to less than or equal to about3.0 mol. %. In other embodiments, the glass composition comprises ZnO inconcentrations from greater than or equal to about 1.5 mol. % to lessthan or equal to about 2.5 mol. %.

In embodiments, the glass composition can comprise fining agents, suchas, for example, SnO₂, sulfates, chlorides, bromides, Sb₂O₃, As₂O₃, andCe₂O₃. In embodiments, the glass composition can comprise fining agentsin concentrations from greater than or equal to 0.0 mol. % to less thanor equal to about 1.0 mol. %, such as from greater than or equal toabout 0.002 mol. % to less than or equal to about 0.9 mol. %. In otherembodiments, the glass composition can comprise fining agents inconcentrations from greater than or equal to about 0.05 mol. % to lessthan or equal to about 0.8 mol. %, such as from greater than or equal toabout 0.1 mol. % to less than or equal to about 0.7 mol. %. In yet otherembodiments, the glass composition can comprise fining agents inconcentrations from greater than or equal to about 0.1 mol. % to lessthan or equal to about 0.3 mol. %, such as about 0.15 mol. %. Inembodiments that use sulfates as the fining agents, the sulfates can beincluded in amount from greater than or equal to about 0.001 mol. % toless than or equal to about 0.1 mol. %.

Accordingly, in some embodiments, the glass composition may comprisegreater than or equal to about 50.0 mol. % to less than or equal toabout 65.0 mol. % SiO₂, greater than or equal to about 14.0 mol. % toless than or equal to about 22.0 mol. % Al₂O₃, greater than or equal toabout 14.0 mol. % to less than or equal to about 22.0 mol. % R₂O, andgreater than or equal to about 4.0 mol. % to less than or equal to about10.0 mol. % P₂O₅. It should be understood that all molar percentageswithin the above ranges are envisioned and included in this disclosure.

Specific glass compositions according to embodiments are in Table 1below.

TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 SiO₂ mol % 52 54 56 58 5060 58 60 58 59 60 59.9 59.9 B₂O₃ 4 0 0 0 0 0 5 4 2 1 0 4 4 Al₂O₃ 22 2322 21 27 20 16 16 20 20 20 16 16 P₂O₅ 6 7 6 5 7 4 5 4 4 4 4 4 4 Na₂O 1414 14 14 14 14 14 14 14 14 14 15.5 15.5 K₂O 2 2 2 2 2 2 2 2 2 2 2 0.50.5 As₂O₃ 0 0 0 0 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 0 0 0 0 0 Li₂O0 0 0 0 0 0 0 0 0 0 0 0 0 MgO 0 0 0 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 00 0 0 0 0 0 0 SnO₂ 0 0 0 0 0 0 0 0 0 0 0 0.1 0.1 ZrO₂ 0 0 0 0 0 0 0 0 00 0 0.02 0.02 CaO P₂O₅ + R₂O/ 1.18182 1 1 1 0.85185 1 1 1 0.909090.95238 1 1 1 Al₂O₃ + B₂O₃ Al₂O₃ + B₂O₃/ 1.625 1.438 1.375 1.313 1.68751.25 1.313 1.25 1.375 1.3125 1.3 1.25 1.25 R₂O 14 18 19 20 21 25 33 3439 42 55 62 63 Density 2.3915 2.424 2.397 2.406 2.42 2.379 2.366 2.40062.3917 (g/cm³) Archimedes Molar Volume 31.59 31.52 31.36 30.7 30.0430.39 30.15 30.36 30.43 (cm³/mol) Calc Young's 80.5 Modulus (GPa)Makashima MacKenzie Young's 69.2 63.91 Modulus RUS (GPa) Shear 28.426.13 Modulus RUS (GPa) Poissons 0.217 0.223 Ratio RUS Pre-IX Vickers1000-2000 1000-2000 1000-2000 Crack Initiation Load (gf) DSC GlassTransition Temperature (° C.) CTE (10{circumflex over ( )}-7) (1/K)Liquidus >1250 >1250 930 750 775 770 775 780 Temperature (° C.) Example14 15 16 17 18 19 20 21 22 23 24 25 SiO₂ mol % 59.88 60 62 62 58 58 5858 60 60 60 60 B₂O₃ 4 4.5 2.5 4.5 4.5 6.5 4.5 4.5 2.5 4.5 6.5 2.5 Al₂O₃16 15.5 15.5 15.5 17.5 15.5 16 15.5 17.5 17.5 15.5 15.5 P₂O₅ 4 4 4 4 4 46 4 4 4 4 6 Na₂O 15.5 15.5 15.5 13.5 15.5 15.5 16 17.5 15.5 13.5 13.515.5 K₂O 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 As₂O₃ 0 0 0 0 00 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 0 0 0 0 0MgO 0 0 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 0 0 0 SnO₂ 0.1 0 0 0 00 0 0 0 0 0 0 ZrO₂ 0.02 0 0 0 0 0 0 0 0 0 0 0 CaO P₂O₅ + R₂O/ 1 11.11111 0.9 0.90909 0.90909 1.1 1.1 1 0.81818 0.81818 1.22222 Al₂O₃ +B₂O₃ Al₂O₃ + B₂O₃/ 1.25 1.25 1.125 1.42857 1.375 1.375 1.3 1.11111 1.251.57143 1.57143 1.125 R₂O 64 72 74 76 77 78 79 80 81 83 88 89 Density2.391 2.363 2.386 2.39 2.372 2.356 2.384 (g/cm³) Archimedes Molar Volume29.51 29.92 30.00 29.8 30.16 30.09 30.28 (cm³/mol) Calc Young's Modulus(GPa) Makashima MacKenzie Young's 63 62 Modulus RUS (GPa) Shear 25 25.9Modulus RUS (GPa) Poissons 0.21 0.21 Ratio RUS Pre-IX Vickers CrackInitiation Load (gf) DSC Glass Transition Temperature (° C.) CTE(10{circumflex over ( )}-7) (1/K) Liquidus 790 780 790 Temperature (°C.) Example 26 27 28 29 30 31 32 33 34 35 36 SiO₂ mol % 60 60 60 60 6056 58 61 59 57 62 B₂O₃ 2.5 4.5 4.5 4.5 4.5 3.5 3 0 0 0 0 Al₂O₃ 15.5 15.515.4 15.4 15.4 17 16.5 15.5 16.5 17.5 15.5 P₂O₅ 4 6 4 4 4 4 4 7 7 7 6Na₂O 17.5 13.5 15.5 16 15.5 19.5 18.5 16.5 17.5 18.5 16.5 K₂O 0.5 0.50.5 0 0.5 0 0 0 0 0 0 As₂O₃ 0 0 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 00 0 Li₂O 0 0 0 0 0 0 0 0 0 0 0 MgO 0 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 00 0 0 0 0 SnO₂ 0 0 0.1 0.1 0.1 0 0 0 0 0 0 ZrO₂ 0 0 0 0 0 0 0 0 0 0 0CaO 0 0 0 0 0 0 P₂O₅ + R₂O/ 1.22222 1 1.00503 1.00503 1.00503 1.146341.15385 1.51613 1.48485 1.45714 1.45161 Al₂O₃ + B₂O₃ Al₂O₃ + B₂O₃/ 11.42857 1.24375 1.24375 1.24375 1.05128 1.05405 0.93939 0.94286 0.945950.93939 R₂O 90 91 93 94 98 107 110 113 114 115 116 Density 2.411 2.3592.388 2.388 2.388 2.42 2.414 2.388 2.401 2.412 2.393 (g/cm³) ArchimedesMolar Volume 29.28 30.67 29.63 29.56 29.63 29.41 29.37 30.41 30.43 30.4730.01 (cm³/mol) Calc Young's Modulus (GPa) Makashima MacKenzie Young's63.4 Modulus RUS (GPa) Shear 26.1 Modulus RUS (GPa) Poissons 0.215 RatioRUS Pre-IX Vickers Crack Initiation Load (gf) DSC Glass TransitionTemperature (° C.) CTE (10{circumflex over ( )}-7) (1/K) Liquidus 785790 730 740 790 775 740 730 770 Temperature (° C.) Example 37 38 39 4041 42 43 44 45 46 47 SiO₂ mol % 60 58 58.8 58.8 60 60 60 60 55 57.9 57.9B₂O₃ 0 0 4 4 4 4 5 5 0 5.25 5.25 Al₂O₃ 16.5 17.5 16.3 16.3 15.75 15.7514 14 15 15.5 15.5 P₂O₅ 6 6 4 4 4 4 5 5 5 5.25 5.25 Na₂O 17.5 18.5 16.416.9 15.75 16.25 13 14 15 14 14 K₂O 0 0 0.5 0 0.5 0 3 2 10 2 2 As₂O₃ 0 00 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 0 0 0 0MgO 0 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 0 0 SnO₂ 0 0 0 0 0 0 0 00 0.1 0.1 ZrO₂ 0 0 0 0 0 0 0 0 0 0 0 CaO 0 0 0 0 0 0 0 0 0 0 0 P₂O₅ +R₂O/ 1.42424 1.4 1.02956 1.02956 1.02532 1.02532 Al₂O₃ + B₂O₃ Al₂O₃ +B₂O₃/ 0.94286 0.94595 1.20118 1.20118 1.21539 1.21539 R₂O 117 118 119120 121 122 127 128 130 131 132 Density 2.406 2.416 2.395 2.394 2.3892.388 2.381 (g/cm³) Archimedes Molar Volume 30.03 30.08 29.67 29.6129.64 29.58 30.35 (cm³/mol) Calc Young's Modulus (GPa) MakashimaMacKenzie Young's Modulus RUS (GPa) Shear Modulus RUS (GPa) PoissonsRatio RUS Pre-IX Vickers Crack Initiation Load (gf) DSC Glass TransitionTemperature (° C.) CTE (10{circumflex over ( )}-7) (1/K) Liquidus 790770 730 Temperature (° C.) Example 48 49 50 51 52 53 54 55 56 57 58 SiO₂mol % 58 58 58 56 54 52 60 60 60 60 60 B₂O₃ 5 5 5 6 7 8 0 0 0 0 0 Al₂O₃16 15.75 15.75 16 16 16 16 16 16 16 16 P₂O₅ 5 5 5 6 7 8 5 5 6 6 7 Na₂O14 13.75 13.75 14 14 14 16 16 16 16 16 K₂O 2 2 2 2 2 2 0 0 0 0 0 As₂O₃ 00 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 0 0 00 MgO 0 0.5 0 0 0 0 3 0 2 0 1 ZnO 0 0 0.5 0 0 0 0 3 0 2 0 SnO₂ 0 0 0 0 00 0 0 0 0 0 ZrO₂ 0 0 0 0 0 0 0 0 0 0 0 CaO 0 0 0 0 0 0 0 0 0 0 0 P₂O₅ +R₂O/ Al₂O₃ + B₂O₃ Al₂O₃ + B₂O₃/ R₂O 133 134 135 136 137 138 139 140 141142 143 Density 2.379 2.381 2.387 2.373 2.369 2.363 2.417 2.453 2.4062.428 2.393 (g/cm³) Archimedes Molar Volume 30.85 31.29 31.76 29.2129.28 29.76 29.83 30.35 (cm³/mol) Calc Young's Modulus (GPa) MakashimaMacKenzie Young's Modulus RUS (GPa) Shear Modulus RUS (GPa) PoissonsRatio RUS Pre-IX Vickers Crack Initiation Load (gf) DSC Glass TransitionTemperature (° C.) CTE (10{circumflex over ( )}-7) (1/K) Liquidus 730785 800 775 765 790 960 Temperature (° C.) Example 59 60 61 62 63 64 6566 67 68 69 SiO₂ mol % 60 62 62.5 63 63.5 64 64.5 62 62.5 63 63.5 B₂O₃ 00 0 0 0 0 0 0 0 0 0 Al₂O₃ 16 15 15 14.5 14.5 14 14 15 15 14.5 14.5 P₂O₅7 5 5 5 5 5 5 4 4 4 4 Na₂O 16 15 15 14.5 14.5 14 14 15 15 14.5 14.5 K₂O0 0 0 0 0 0 0 0 0 0 0 As₂O₃ 0 0 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 00 0 Li₂O 0 0 0 0 0 0 0 0 0 0 0 MgO 0 3 2.5 3 2.5 3 2.5 4 3.5 4 3.5 ZnO 10 0 0 0 0 0 0 0 0 0 SnO₂ 0 0 0 0 0 0 0 0 0 0 0 ZrO₂ 0 0 0 0 0 0 0 0 0 00 CaO 0 0 0 0 0 0 0 0 0 0 0 P₂O₅ + R₂O/ Al₂O₃ + B₂O₃ Al₂O₃ + B₂O₃/ R₂O144 145 146 147 148 149 150 151 152 153 154 Density 2.404 (g/cm³)Archimedes Molar Volume 30.38 (cm³/mol) Calc Young's Modulus (GPa)Makashima MacKenzie Young's Modulus RUS (GPa) Shear Modulus RUS (GPa)Poissons Ratio RUS Pre-IX Vickers Crack Initiation Load (gf) DSC GlassTransition Temperature (° C.) CTE (10{circumflex over ( )}-7) (1/K)Liquidus Temperature (° C.) Example 70 71 72 73 74 75 76 77 78 79 80SiO₂ mol % 64 64.5 60 62 63 61.5 63 60.5 60.5 61 61 B₂O₃ 0 0 0 0 0 0 0 00 0 0 Al₂O₃ 14 14 15.95 14.95 14.45 15 14 15.5 15.25 15.25 15 P₂O₅ 4 4 55 4 5 5 5 5 5 5 Na₂O 14 14 15.95 14.95 14.45 15 14 15.5 15.25 15.25 15K₂O 0 0 0 0 0 0 0 0 0 0 0 As₂O₃ 0 0 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 00 0 0 0 Li₂O 0 0 0 0 0 0 0 0 0 0 0 MgO 4 3.5 3 3 4 3.5 4 3.5 4 3.5 4 ZnO0 0 0 0 0 0 0 0 0 0 0 SnO₂ 0 0 0.1 0.1 0.1 0 0 0 0 0 0 ZrO₂ 0 0 0 0 0 00 0 0 0 0 CaO 0 0 0 0 0 0 0 0 0 0 0 P₂O₅ + R₂O/ Al₂O₃ + B₂O₃ Al₂O₃ +B₂O₃/ R₂O 155 156 157 158 159 160 161 162 163 164 165 Density 2.41 2.4192.417 (g/cm³) Archimedes Molar Volume (cm³/mol) Calc Young's Modulus(GPa) Makashima MacKenzie Young's Modulus RUS (GPa) Shear Modulus RUS(GPa) Poissons Ratio RUS Pre-IX Vickers Crack Initiation Load (gf) DSCGlass Transition Temperature (° C.) CTE (10{circumflex over ( )}-7)(1/K) Liquidus Temperature (° C.) Example 81 82 83 84 85 86 87 88 89 90SiO₂ mol % 62 62 60.5 60 60.5 56 58 52 58 59 B₂O₃ 0 0 0 0 0 0 0 4 2 1Al₂O₃ 14.75 14.5 14.8 15.5 15.25 22 21 22 20 20 P₂O₅ 5 5 5 5 5 6 5 6 4 4Na₂O 14.75 14.5 15.7 16.5 15.25 14 14 14 14 14 K₂O 0 0 0 0 0 2 2 2 2 2As₂O₃ 0 0 0 0 0 0 0 0 0 0 Cs₂O 0 0 0 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 00 0 MgO 3.5 4 4 3 4 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 0 SnO₂ 0 0 0 0 0 0 00 0 0 ZrO₂ 0 0 0 0 0 0 0 0 0 0 CaO 0 0 0 0 0 0 0 0 0 0 P₂O₅ + R₂O/Al₂O₃ + B₂O₃ Al₂O₃ + B₂O₃/ R₂O 166 167 168 169 170 Density (g/cm³)Archimedes Molar Volume (cm³/mol) Calc Young's Modulus (GPa) MakashimaMacKenzie Young's Modulus RUS (GPa) Shear Modulus RUS (GPa) PoissonsRatio RUS Pre-IX Vickers Crack Initiation Load (gf) DSC Glass TransitionTemperature (° C.) CTE (10{circumflex over ( )}-7) (1/K) LiquidusTemperature (° C.)

Glasses according to embodiments disclosed herein may be formed intoglass articles, such as, for example, glass sheets. In embodiments, theglass composition has a liquidus viscosity of at least 130 kilopoise andis down-drawable by suitable techniques, for example, but not limitedto, fusion-draw processes, slot-draw processes, and re-draw processes.In other embodiments the glass sheet can be made by the float process.Three dimensional glass articles may be made by, for example, molding,blow molding, and the like.

The glass composition may be formed into glass sheets having anythickness. For example, for embodiments used in electronic devices suchas touch screens or a touch screen cover glasses for cell phones,computers (including laptops and tablets) and ATMs, the glass sheet mayhave a thickness in the range of 0.2 mm to 3 mm. In other embodimentsthe glass sheet may have a thickness in the range of 0.2 mm to 2.0 mm.In further embodiments, the glass sheet may have a thickness in therange of 0.3 mm to 0.7 mm. Other applications of glasses according toembodiments include use as table tops or cover tops, shelving inrefrigerators or for storage shelves or shelf covers in, for example,laboratories, hospitals and other facilities where antimicrobialproperties are desired. It should be noted that the glass can be thickeraccording to the intended use. For example, for a hospital bench top orbench top cover, it may be desirable that the glass have a thickness ofgreater than 3 mm.

Glass Strengthening

According to embodiments, the glass compositions may be strengthened,such as, for example, by physical and/or chemical tempering. In someembodiments, the glass composition may be strengthened by ion exchange.Glass compositions that are amenable to ion exchange typically containsmaller monovalent alkali metal ions, such as, for example, Na and/or Liions, that can be exchanged by larger monovalent ions, such as, forexample, K, Rb, Cs, and/or Ag ions. Exemplary glass compositions thatare amenable to ion exchange are discussed above.

Embodiments include strengthening a glass article, such as a glasssheet, in a two-step (2-step) method. The 2-step method of embodimentsuses a first ion-exchange bath containing an ion-exchanging alkali metalcompound with ions larger than the alkali metal ions in the glassarticle (e.g., exchanging Na ions in the glass article for K ions in anion-exchange bath), followed by ion-exchange using a second ion-exchangebath containing an anti-microbrial agent such as silver. In someembodiments, the glass article may be exposed to the silver-containingion-exchange bath for a much shorter time than the first ion-exchangebath. The silver ion-exchange bath may contain a high concentration ofboth silver ions and, optionally, an ion-exchanging alkali metalcompound whose ions are larger than the alkali metal ions in the glassarticle.

In a first step of a 2-step method according to embodiments, the largeralkali metal ions are exchanged into the glass to form a glass articlehaving a compressive stress. In embodiments, the glass article may beexposed to the ion-exchange bath for a time greater than or equal toabout 3 hours at a temperature from greater than or equal to about 300°C. to less than or equal to about 500° C. In some embodiments, the glassarticle may be exposed to the ion-exchange bath at a temperature of fromgreater than or equal to about 350° C. to less than or equal to about450° C. and for a duration of from greater than or equal to about 40minutes to less than or equal to about 6 hours, such as from greaterthan or equal to about 1.0 hour to less than or equal to about 5 hours.This first step increases the compressive stress of the glass article byreplacing smaller ions in the glass matrix, such as Na ions, with largerions, such as, for example, K ions. In embodiments, the ion-exchangebath for the first step of the 2-step method may include one or more ofNaNO₃ and KNO₃. In some embodiments, the ion-exchange bath for the firststep of the 2-step method may be KNO₃. Suitable ion exchange processesfor the first step of the 2-step method are disclosed in U.S. Pat. No.5,674,790, which is herein incorporated by reference in its entirety.

In the second step of the 2-step ion exchange method, silver ions areexchanged into the surface of the glass article and replace the alkalimetal ions in the glass to a shallow enough depth so that there is notsignificant loss or relaxation of the compressive stress which wasincreased during the first step of the ion exchange process. Inembodiments, the ion-exchange bath of the second step may primarilycomprise Ag-containing compounds, such as, for example AgNO₃. In otherembodiments of the 2-step method, the second step may include alkalimetal containing compounds in addition to Ag-containing compounds. Inembodiments, the same alkali metal containing compound may be used inboth the first and second ion-exchange baths. Thus, in some embodiments,the second step of the 2-step method includes exposing the glass articleto an ion exchange bath comprising AgNO₃ and KNO₃.

The ion-exchange bath in the second step of the 2-step method may, inembodiments, include from greater than or equal to about 5.0 mol. % toless than or equal to 100 mol. % Ag-containing compounds, such as, forexample, AgNO₃. In some embodiments, the second step of the 2-stepmethod may include from greater than or equal to about 10 mol. % to lessthan or equal to 95 mol. % Ag-containing compounds, such as from greaterthan or equal to about 15 mol. % to less than or equal to about 90 mol.% Ag-containing compounds. In other embodiments, the second step of the2-step method may include from greater than or equal to about 20 mol. %to less than or equal to 85 mol. % Ag-containing compounds, such as fromgreater than or equal to about 25 mol. % to less than or equal to about80 mol. % Ag-containing compounds. In yet other embodiments, the secondstep of the 2-step method may include from greater than or equal toabout 30 mol. % to less than or equal to 75 mol. % Ag-containingcompounds, such as from greater than or equal to about 35 mol. % to lessthan or equal to about 70 mol. % Ag-containing compounds. In each of theabove embodiments, the remainder of the ion-exchange bath compositionmay be one or more alkali metal compounds, such as, for example, KNO₃and/or NaNO₃.

In embodiments, the duration of the ion-exchange time using thesilver-containing bath may be less than or equal to about 30 minutes,which may produce a shallow depth of exchange, such as less than 20 μm.In some embodiments the ion-exchange time is from greater than or equalto 0.0 minutes to less than or equal to about 20 minutes. In otherembodiments, the ion-exchange time is from greater than or equal to 0.0minutes to less than or equal to about 10 minutes. The ion-exchange iscarried out at a temperature from greater than or equal to about 370° C.to less than or equal to about 450° C., such as at a temperature fromgreater than or equal to about 400° C. to less than or equal to about440° C. Without being bound to any specific theory, the 2-step method ofion exchange provides the glass with only a surface concentration ofAg⁺¹ to facilitate the antimicrobial effect as having the silverpenetrate to greater depths adds nothing to the antimicrobial orantibacterial effect since silver ions do not move or migrate within theglass at the typical end-use application temperatures. The 2-step methodthus allows one to obtain a significantly higher concentration of Ag⁺¹ions on the surface of the glass which results in a commensuratedecrease in the “kill” time (the time to reach a log 3 reduction inmicrobes) while not producing any undesirable yellow color or decreasingthe compressive stress of the glass article by replacing deeplypositioned alkali metal ions with smaller Ag ions.

In embodiments, the glass article may have a maximum concentration of Agions within 60 nm of a free surface of the glass article, such as within50 nm of a free surface of the glass article. In other embodiments, theglass article may have a maximum concentration of Ag ions within 40 nmof a free surface of the glass article, such as within 30 nm of the freesurface of the glass article. As used herein, “free surface” is used toindicate a surface of the glass article that is exposed and intended tobe exposed in the final use of the glass article.

The quantitative knowledge of the surface Ag ion concentration isdesired to ascertain the effectiveness of the antimicrobial action. Thisis even more pertinent in the present case where the Ag is being addedby an ion-exchange process. In embodiments, the glass article maycomprise an average concentration of Ag within 60 nm of a free surfaceof the glass greater than or equal to about 10 mol. % to less than orequal to about 15 mol. %, such as greater than or equal to about 12 mol.% to less than or equal to about 14 mol. %. The analytical techniquesXPS (X-ray photoluminescence spectroscopy) and SIMS (secondary ion massspectroscopy) can be used to obtain the Ag ion profile, but they yieldvolume concentration values, albeit close to the surface, whereas whatis important is the surface ion concentration. XPS can quantitativelydetermine the Ag ion concentration to within 10-20 nm.

In embodiments, the depth of a compressive stress layer formed by the2-step ion exchange method may be from greater than or equal to about 20μm less than or equal to about 60 μm, such as from greater than or equalto about 25 μm less than or equal to about 55 μm. In other embodiments,the depth of a compressive stress layer formed by the 2-step ionexchange method may be from greater than or equal to about 30 μm lessthan or equal to about 50 μm, such as from greater than or equal toabout 35 μm less than or equal to about 45 μm. In yet other embodiments,the depth of a compressive stress layer formed by the 2-step ionexchange method may be from greater than or equal to about 40 μm lessthan or equal to about 50 μm. In embodiments, the compressive stress ofthe glass article formed by the 2-step ion exchange method may begreater than or equal to about 700 MPa, such as greater than or equal toabout 800 MPa. In other embodiments, the compressive stress of the glassarticle formed by the 2-step method may be greater than or equal toabout 900 MPa. In embodiments, the compressive stress of the glassarticle formed by the 2-step ion exchange method may be less than orequal to about 1100 MPa.

Without being bound to any particularly theory, it is believed thatthere is minimal impact on the compressive stress using the 2-stepmethod, because the depth of the Ag ion exchange into the glass in thesecond step is shallow. Therefore, the compressive stress of the glass,which was chemically strengthened in a first step by ion-exchange oflarger ions, such as, for example K or larger alkali metal ions, forsmaller ions in the glass, such as, for example, Na and/or Li ions, thecompressive stress of the glass is not measurably affected. Further, itis noted that the ionic radius of silver and potassium ions are similar,the Pauling ionic radii of silver and potassium being 1.26 and 1.33Angstroms, respectively. Consequently, an ion-exchange of silver ionsfor potassium ions already in the glass after the first stepion-exchange will have a minimal effect on the compressive stress of theglass.

In embodiments, the glass may have a light transmission, uncorrected forreflection losses, over wavelengths from greater than or equal to about400 nm to less than or equal to about 750 nm, of greater than or equalto about 85%. In some embodiments, the glass may have a lighttransmission, uncorrected for reflection losses, over wavelengths fromgreater than or equal to about 400 nm to less than or equal to about 750nm, from greater than or equal to about 85% to less than or equal toabout 92%, such as from greater than or equal to about 88% to less thanor equal to about 90%.

Antimicrobial Efficacy

As used herein the term “antimicrobial,” means an agent or material, ora surface containing the agent or material that will kill or inhibit thegrowth of microbes from at least two of the families consisting ofbacteria, viruses, and fungi. The term as used herein does not mean itwill kill or inhibit the growth of all microbe species within suchfamilies, but that it will kill or inhibit the growth or one or morespecies of microbes from such families.

As used herein the term “Log Kill” means −Log (C_(a)/C₀), whereC_(a)=the colony form unit (CFU) number of the antimicrobial surfacecontaining silver ions and C₀=the colony form unit (CFU) of the controlglass surface that does not contain silver ions. That is:Log Kill=−Log(C _(a) /C ₀).As an example, a Log Kill of 4=99.99% of the bacteria or virus killedand a Log Kill of 6=99.9999% of bacteria or virus killed.

According to embodiments, the antimicrobial activity of the glassarticles when measured at high relative humidity (RH), such as, forexample, RH greater than or equal to about 90%, and physiologicaltemperatures, such as, about 37° C., when measured using JIS ZInternational Test, are greater than or equal to about 5 Log Kill, suchas greater than or equal to about 6 Log Kill.

Glass articles according to this disclosure not only have antimicrobialactivity at high temperatures and relative humidity, but also haveantimicrobial activity at ambient conditions. The antimicrobial activityof glass articles according to embodiments measured at room temperature(i.e., about 23° C.) and low relative humidity (i.e., about 40%)measured according to the EPA testing protocol may be greater than orequal to about 1.0 Log Kill, such as greater than or equal to about 1.2Log Kill. In some embodiments, the antimicrobial activity of glassarticles may be greater than or equal to about 1.4 Log Kill, such asgreater than or equal to about 1.6 Log Kill. In other embodiments, theantimicrobial activity may be greater than or equal to about 1.8 LogKill.

Coatings

Embodiments may include a functional coating on the antimicrobial,chemically strengthened glass. For example, in many touch screenapplications (phones, computers, ATMs, etc) where the glass is used as acover glass, a coating or film is placed on the glass surface so thatfingerprints can be cleaned relatively easily. The coating(s) thatfacilitate cleaning are low surface energy coatings. In embodiments, thecoatings may include fluoroalkylsilanes coatings having a generalformula A_(x)-Si—B_(4-x), where: A is selected from the group consistingof perfluoroalkyl R_(F)—, perfluoroalkyl terminated perfluoropolyether,perfluoroalkyl-alkyl, copolymers of fluoroalkene silanes and alkenesilanes, and mixtures of fluoroalkylsilanes and hydrophilic silanes; Bis Cl, acetoxy [CH₃—C(O)—O—] or alkoxy [for example CH₃O— or C₂H₅O—];and x=1 or 2. Low surface energy coatings of the foregoing types arecommercially available from different manufacturers, for example, DowCorning, [DC2634—a perfluoropolyether silane in which the functionalperfluoro moiety is Poly[oxy(1,1,2,2,3,3-hexafluoro-1,3-propanediyl)],α-(heptafluoropropyl)-ω-[1,1,2,2-tetrafluoro-3-(2-propenyloxy)propoxy];Gelest [SIT8174.0, Tridecafluorotetrahydrooctyltrichlorosilane;SIT8371.0, Trifluoropropyltrichlorosilane; SIH5841.0Heptadecafluorotetrahydrodecyl trichlorosilane; and SIH5841.0(heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane; SIH5841.5(heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane; and SIH5841.2(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane]; Cytonix [FSM1200 Perfluoropolyether mono-silane; FSD 2500 Medium molecular weightperfluoropolyether di-silane; FSD 4500 High molecular weightperfluoropolyether polysilanes]. The low surface energy coating may havea spacer or skeletal chain length in from greater than or equal to about1 nm to less than or equal to about 20 nm, the skeletal chain beingcarbon atoms or a mixture of carbon and oxygen atoms in the case of theperfluoropolyethers. In some embodiments the chain length is fromgreater than or equal to about 2 nm to less than or equal to about 15nm. In other embodiment the chain length is from greater than or equalto about 3 nm to less than or equal to about 10 nm.

Other examples of low surface energy coatings are (a) copolymers offluoroalkene silanes and alkene silanes; and (b) mixtures offluoroalkylsilanes and hydrophilic silanes.

In embodiments, silanes other than the foregoing can also be usedprovided that they do not prevent water vapor from reaching the surfaceof the glass so that silver ions can be transported from the glasssurface to the microbe to thereby kill the microbe or inhibit itsgrowth.

Generally, embodiments of the fluoro-containing coatings describe abovehave 1 or 2 fluorocarbon-containing moieties attached to the silicon andeach of the moieties, independently, have a chain length in the range of1 nm to 20 nm. In embodiments, the chain may include oxygen atoms orsulphur atoms. In embodiments, the chain length may be from greater thanor equal to about 1 nm to less than or equal to about 20 nm, such asfrom greater than or equal to about 2 nm to less than or equal to about10 nm. According to some embodiments, at least part the fluorocarbonmoiety be sufficiently distant from the surface so that water moleculescan come into contact with the surface, pick up silver ions on thesurface, and transport the silver ions to a microbe where they can beabsorbed in to microbe and thus kill it or decrease its reproductiverate. Consequently, it is preferred that one or two fluorocarbonmoieties be attached to the silicon atom and that the silicon atom bebonded to the glass by two or three Si—O bonds. For example, if thealkyl group of (a) above, which functions as a spacer or skeletal chainbetween the silver-containing glass surface and the fluorocarbon moiety,is too short, then a hydrophobic fluorocarbon moiety can block watermolecules from reaching the glass surface and thus silver ions cannot betransported from the surface to and into the microbe. In anotherinstance, without being constrained by any particular theory, it isbelieved that the oxygen atoms in a perfluoropolyether alkoxy silanethat has been bonded to the surface of the antimicrobial glass canfacilitate the migration of water molecules by oxygen atoms along thechain to the surface where the water molecules can coordinate to silverions and facilitate the ion transport to the microbe. An exemplaryperfluoropolyether alkoxy silane is Dow Corning® 2634 used as 0.02-1 wt% solutions in a fluorinated solvent. After the coating material wasapplied to the antimicrobial glass article such as described herein, thecoating was cured to adhere the coating to the surface of the glassarticle and finally sonicated in a fluorinated solvent (for example,Novec™ HFE7200, 3M Company) bath for a 3 minutes remove any unreactedcoating material. The curing was done thermally by either heating thecoated articles in an oven, for example, at 50° C., 50% RH, for a curetime as suggested by the manufacturer or by infrared heating of thecoated articles. The coated article was then heated in an oven for atime in the range of 30 minutes to 2 hours to cure the coating materialto the glass surface.

The method and process for the deposition of these coatings are capableof controlling the thickness and morphology of the coating on thesurface of the glass. Process methods and steps can be introduced wherethe coating was deposited in such a fashion either to be discontinuousor quasi-discontinuous. Such process methods include, but are notlimited to, vapor deposition or spray coating through a predeterminedcoverage mask, ink jet printing, micro contact printing using a masterwhich would allow the fluorosilane to be coated in specific regions, andhumidity curing to allow phase separation of the fluorosilane. When thecoating is sufficiently thin it can be continuous. Thin continuouscoatings can be deposited, for example, by dip, spray and vapordeposition followed by curing to adhere the silanes, and followed byultrasound cleaning to remove un-reacted but physically adsorbedsilanes. The foregoing procedures allow the antimicrobial action topersist in open uncoated areas, or in areas where the coating is verythin or the surface is coating-free while at the same time maintainingintended functional performance of the coating. In embodiments, thethickness of the coating is from greater than or equal to about 0.5 nmto less than or equal to about 5 nm. In other embodiments the thicknessof the coating is from greater than or equal to about 1 nm to less thanor equal to about 3 nm. In the thin coating case a mixed self-assembledmonolayer can be prepared on the surface using two silanes, where onesilane is a fluoroalkylsilane and the other silane is a hydrophilicsilane (for example, a polyethylene glycol containing silane), whereinthe hydrophilic or “water loving” silane domains assist in theantimicrobial action by capturing water molecules and presenting them tothe surface where the water can pick up silver ions for transport to themicrobe. In one embodiment fluoro-oligoethylene glycol silanes can alsobe used, where the oligoethylene glycol part of the silanes can assistin capturing free water at the interface.

EXAMPLES

Embodiments will be further clarified by the following examples.

Example 1

Example 1 tests the strength of five glass samples with a ring-on-ringtest. All five glass samples are 1.0 mm thick glass sheets made fromCorning 5318 glass. For Comparative Sample 1, the glass is preparedusing a one-step ion exchange method with a KNO₃ bath. Samples 1-4 areprepared using a 2-step ion exchange method first using a KNO₃ bath,followed by a bath of KNO₃ and AgNO₃.

As shown in FIG. 1, Comparative Sample 1, which is prepared using aone-step ion exchange, fails at a load of approximately 525 kg. Samples1-4, which are prepared using a 2-step ion exchange comprising Ag ions,fail at loads from approximately 250 Kg to approximately 475 Kg. Thus,the samples show that glasses prepared using a 2-step ion exchangemethod can be prepared to have strengths approximately equal to glassesprepared using a one-step ion exchange method. This was previouslyunexpected because replacing large alkali metal ions, such as K⁺, withAg ions, as is done in the second step of the 2-step ion exchangemethod, was traditionally thought to lower the strength of the glassarticle.

Example 2

Example 2 tests antimicrobial activity of three glass samples. All threeglass samples are 1.0 mm thick Corning 5318 glass sheets. All threeglass samples are ion exchanged in a KNO₃ molten salt bath at 420° C.for 2.5 hours. Subsequently, the three glass samples are subjected to asecond ion exchange in an ion exchange bath comprising Ag. ComparativeSample 2 is subjected to a 20% Ag and 80% KNO₃ ion exchange bath. Sample5 is subjected to a 100% Ag/K ion exchange bath. Sample 6 is subjectedto a 100% Ag/K ion exchange bath.

As shown in FIG. 2, Comparative Sample 2 has a Log Kill of about 1.4,Sample 5 has a Log Kill of about 1.8, and Sample 6 has a Log Kill ofabout 1.6. Thus, these glass samples show that 100% Ag/K ion exchangebaths provide better antimicrobial protection at low relative humidityand temperature than 20% Ag ion exchange baths.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A strengthened antimicrobial glass comprising:SiO₂; Al₂O₃; R₂O, wherein R is an alkali metal; and P₂O₅, wherein: theglass comprises a compressive stress layer having a thickness of greaterthan or equal to about 20 μm and having a surface compressive stress;and the glass has an antimicrobial activity greater than or equal toabout 1.0 Log Kill at about 23° C. and about 40.0% relative humidity. 2.The glass of claim 1, wherein the surface compressive stress is greaterthan or equal to about 700 MPa.
 3. The glass of claim 1, wherein theglass further comprises Ag.
 4. The glass of claim 3, wherein the glasshas a maximum concentration of Ag within 60 nm of a free surface of theglass.
 5. The glass of claim 3, wherein an average concentration of Agwithin 60 nm of a free surface of the glass is greater than or equal toabout 10 mol. % to less than or equal to about 15 mol. %.
 6. The glassof claim 3, wherein the glass has a light transmission of greater thanor equal to about 85% over wavelengths from greater than or equal toabout 400 nm to less than or equal to about 750 nm.
 7. The glass ofclaim 1, wherein the glass has a molar ratio of Al₂O₃ to R₂O that isgreater than or equal to about 0.5:1 to less than or equal to about1.5:1.
 8. The glass of claim 1, wherein the glass further comprisesgreater than 0.0 mol. % to less than or equal to about 4.0 mol. % ZnO.9. The glass of claim 1, wherein the glass has an antimicrobial activitygreater than or equal to about 5.0 Log Kill at about 37° C. and arelative humidity greater than or equal to about 90%.
 10. The glass ofclaim 1, wherein R is selected from the group consisting of Li, Na, andK.
 11. The glass of claim 1, wherein the compressive stress layer has adepth of greater than or equal to about 40 μm to less than or equal toabout 50 μm.
 12. The glass of claim 1, wherein the glass has acompressive stress of greater than or equal to about 900 MPa.
 13. Theglass of claim 1, further comprising greater than 0.0 mol. % to lessthan or equal to about 4.0 mol. % alkaline earth metal.
 14. The glass ofclaim 1, further comprising a fluorosilane coating on a free surface ofthe glass.
 15. The glass of claim 14, wherein the coating has a generalformula of:A_(x)-Si—B_(4-x), where A is selected from the group consisting ofperfluoroalkyl, perfluoroalkyl terminated perfluoropolyether,perfluoroalkyl-alkyl, copolymers of fluoroalkene silanes and alkenesilanes, and mixtures of fluoroalkylsilanes and hydrophilic silanes; andB is selected from the group consisting of Cl, acetoxy, and alkoxy; andx=1 or
 2. 16. The glass of claim 1, wherein the glass comprises greaterthan or equal to about 50.0 mol. % to less than or equal to about 65.0mol. % SiO₂.
 17. The glass of claim 1, wherein the glass comprisesgreater than or equal to about 14.0 mol. % to less than or equal toabout 22.0 mol. % Al₂O₃.
 18. The glass of claim 1, wherein the glasscomprises greater than or equal to about 14.0 mol. % to less than orequal to about 22.0 mol. % R₂O.
 19. The glass of claim 1, wherein theglass comprises greater than or equal to about 4.0 mol. % to less orequal to about 10.0 mol. % P₂O₅.
 20. A method for making strengthenedantimicrobial glass, the method comprising: obtaining a glass articlecomprising: SiO₂, Al₂O₃, R₂O, wherein R is an alkali metal, and P₂O₅;strengthening the glass article by contact with a first ion-exchangeliquid; and contacting the glass article with a second ion-exchangeliquid comprising an antimicrobial agent, wherein: the glass comprises acompressive stress layer having a thickness of greater than or equal toabout 20 μm and having a surface compressive stress; and the glass hasan antimicrobial activity greater than or equal to about 1.0 log kill atabout 23° C. and a relative humidity of about 40%.
 21. The method ofclaim 20, wherein the surface compressive stress is greater than orequal to about 700 MPa.
 22. The method of claim 20, wherein thecompressive stress layer has a thickness of less than or equal to about60 μm.
 23. The method of claim 20, wherein the first ion-exchange liquidis selected from the group consisting of NaNO₃, KNO₃, and mixturesthereof.
 24. The method of claim 20, wherein the antimicrobial agentcomprises Ag.
 25. The method of claim 24, wherein the secondion-exchange liquid further comprises a member selected from the groupconsisting of NaNO₃, KNO₃, and mixtures thereof.
 26. The method of claim24, wherein a silver salt concentration in the second ion-exchangeliquid is greater than or equal to about 5.0 mol. %.
 27. The method ofclaim 20, wherein the strengthening step comprises holding the glassarticle in a bath of the first ion-exchange liquid that has atemperature of greater than or equal to about 300° C. to less than orequal to about 500° C. for a duration of greater than or equal to about40 minutes to less than or equal to about 6 hours.
 28. The method ofclaim 20, wherein the glass comprises greater than or equal to about50.0 mol. % to less than or equal to about 65.0 mol. % SiO₂.
 29. Themethod of claim 20, wherein the glass comprises greater than or equal toabout 14.0 mol. % to less than or equal to about 22.0 mol. % Al₂O₃. 30.The method of claim 20, wherein the glass comprises greater than orequal to about 14.0 mol. % to less than or equal to about 22.0 mol. %R₂O.
 31. The method of claim 20, wherein the glass comprises greaterthan or equal to about 4.0 mol. % to less or equal to about 10.0 mol. %P₂O₅.